Japanese imperial year

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The Japanese imperial year (皇紀, kōki) or "national calendar year" is a unique calendar system in Japan.[1] It is based on the legendary foundation of Japan by Emperor Jimmu in 660 BC.[2] Kōki emphasizes the long history of Japan and the Imperial dynasty.[3]


Kōki dating was used as early as 1872, shortly after Japan adopted the Gregorian calendar system,[4] and was popular during the life of the Meiji Constitution (1890–1947).

The Summer Olympics and Tokyo Expo were planned as anniversary events in 1940 (Kōki 2600);[5] but the international games were not held because of the Second Sino-Japanese War.[6]

The Imperial Japanese Army (IJA, from 1927) and Imperial Japanese Navy (IJN, from 1929) used the Kōki system for identification.[7] For example many Japanese names circa World War II use imperial years:

  • The IJA's Type 92 battalion gun was called "ninety-two" because its design was completed in 1932, and the 2592nd year since the first Emperor of Japan was 1932 (Kōki 2592).
  • Japan's wartime cipher machine was named the System 97 Printing Machine for European Characters because it entered service in 1937 (Kōki 2597).
  • The Mitsubishi A6M (Navy Type 0 Carrier Fighter), colloquially called the "Zero" by allied forces, entered service in 1940 (Kōki 2600).

The Proclamation of Indonesian Independence (1945) used the imperial year (Kōki 2605).

In Japan today, the system of counting years from the reign of Emperor Jimmu has been officially abandoned.[8] Now the system is used in Shinto context only.

Related pages


  1. ^ Nussbaum, Louis-Frédéric. (2005). "Kigen" in Japan Encyclopedia, p. 514.
  2. ^ Gubbins, John Harrington. (1922). The Making of Modern Japan, p. 71; Mossman, Samuel. (1873). New Japan, the Land of the Rising Sun, p. 462.
  3. ^ Chamberlain, Bail Hall. (1905). Things Japanese, p. 478; Goodrich, John King. (1913). Our Neighbors: the Japanese, p. 61.
  4. ^ 神武天皇即位紀元二千五百三十三年明治六年太陽暦 (1872)
  5. ^ Ruoff, Kenneth J. (2001). The People's Emperor: Democracy and the Japanese Monarchy, 1945–1995, p. 268 n52.
  6. ^ Organizing Committee of the XIIth Olympiad. (1940). Report of the Organizing Committee on its Work for the XIIth Olympic Games of 1940 in Tokyo until its Relinquishment, pp. 174–175 (PDF 198–199 of 207); retrieved 2012-2-21.
  7. ^ Lacroix, Eric. (1997). "Table A.2. Japanese Dates," Japanese cruisers of the Pacific War, p. 700.
  8. ^ Nussbaum, "Calendar" at pp. 98–99.

External links